1. Field of the Invention
The present invention relates to a liquid-discharge recording apparatus in which a liquid is emitted as liquid droplets and these droplets are deposited on a recorded material such as a paper or the like the to perform recording and, more particularly, to a liquid-discharge recording apparatus in which an emission energy is given to the liquid to form flight liquid droplets.
2. Description of the Prior Art
A liquid-discharge recording method (ink-jet recording method) is a recording method whereby liquid droplets of a recording liquid are formed by various methods and these droplets are deposited on a recorded material such as a paper or the like thereby to perform the recording.
Among recording apparatuses (printers) to which such a recording method is applied, as an apparatus having a structure suitable for constituting a high-density multiorifice of the recording head, a liquid-discharge recording apparatus of the type using the heat as an energy to form emission liquid droplets (hereinafter, referred to as an ink-jet printer) can be mentioned.
Such an ink-jet printer of the type using heat as the liquid droplet emission energy generally comprises liquid droplet forming means and a recording head. Namely, the liquid droplet forming means heats the recording liquid and causes the deformation of the recording liquid accompanied with a rapid increase in volume and allows the recording liquid to be emitted from an orifice (liquid droplet emission hole) of the nozzle portion, thereby forming liquid droplets of the recording liquid. The recording head has an electrothermal energy converting device (hereinafter referred to as an emitting heater) which can generate heat to heat the recording liquid in response to an electrical signal.
On one hand, as a recording liquid which is used to record by the ink-jet printer, a water-base recording liquid is mainly used in consideration of the recording characteristic, safety, and the like. This water-base recording liquid is generally formed from the recording material component such as a pigment, dye, or the like and the water or solvent component mainly consisting of water and water soluble organic solvent in order to dissolve or disperse the recording material component.
In the foregoing printer using the heat as the liquid droplet emission energy and printers to which other liquid droplet forming methods are applied, in many cases, the orifice formed at the end of the nozzle from which the recording liquid is emitted is always open to the outside of the apparatus irrespective of whether the apparatus is driven or not.
Therefore, in the case where the apparatus is not used for recording for a long time, the solvent component of the liquid, such as, for example, water, volatile organic solvent, or the like is evaporated from the orifice into the open air from the recording liquid remaining in the orifice, and the portions near the orifice, since a water-base liquid or other solvent is used in the recording liquid as mentioned above. Thus, the recording material component and the unvolatilizable solvent component remain in the recording liquid, causing a viscosity of the recording liquid remaining in this portion to increase. Since the viscosity of the recording liquid exceeds a range suitable for emission of the recording liquid, there are problems such that immediately after the recording was restarted, in spite of the fact that an emitting signal is applied, a defective emission of liquid droplets in which no liquid droplet is emitted is likely to occur and a failure occurs in an initial printing section or the like of a recording image.
On one hand, although there have been proposed the printers in which the emission surface where the orifice is formed is capped when the apparatus is not used such as in the case where the power supply is off or the like, even if the emission surface is capped, the orifice is not perfectly shut out from the open air. Therefore, the foregoing problems are caused even in this kind of printers.
On the other hand, in Japanese Patent Unexamined Publication No. 187364/1983, there has been proposed the recording method whereby even when the liquid droplet emitting signal is not applied, an electrical signal of such a level that no recording liquid droplet is emitted is always applied to the emitting heater thereby to preheat the recording liquid in a manner such that a temperature of the recording liquid can always be maintained at a value within a predetermined range in order to obtain a good emitting state of liquid droplets for an increase in viscosity of the recording liquid at low temperatures.
Even in the printer to which the above method is applied, however, since the electrical signal is applied to the emitting heater so that the recording liquid is always maintained at high temperatures even during a relatively long interruption or stop interval of the recording operation as well, the solvent component in the recording liquid can be more easily evaporated, so that there is a problem such that the defective liquid droplet emission is further likely to occur at the restart of the recording as mentioned above. In addition, according to this method, since the peripheral portion of the emitting heater is always heated, the following problems are caused. Namely, durability of the peripheral members of the emitting heater is lost. Physical properties of the recording liquid remaining in the peripheral portion of the emitting heater change due to the heat thereof while the recording is interrupted, so that the color of the recording liquid changes or a precipitate is produced in the recording liquid and the orifice is choked, causing defective liquid droplet emission or the like.
In addition, just after the power supply of the printer was turned on, a temperature of the ink liquid regarding the recording depends on the environmental conditions such as ambient temperature and the like. Therefore, it is undesirable to start the recording by emitting the ink immediately after the turn-on of the power supply for the purpose of obtaining the stable printing state.
Therefore, it is considered to constitute the ink-jet printer in a manner such that the preliminary emission is performed before the start of the printing operation after the turn-on of the power supply and the old ink remaining in the head portion of the nozzle is preliminarily discharged and thereby optimizing the emission of the ink.
However, hitherto, the print output is carried out through an IC for a port from a microprocessing unit (MPU) for controlling each section of the printer. Therefore, according to the conventional constitution, it is extremely difficult to finely control such preliminary emission due to a problem of the processing time of the software, so that there is a problem such that the optimum preliminary emission cannot be performed.